Diamond is an allotrope of carbon which is metastable at ordinary pressures, having a large activation energy barrier which prevents conversion to graphite, the more stable allotrope at ordinary temperatures and pressures. In addition to its value as a precious gem, the uses of diamond include use as abrasives in polishes, and in various grinding, saving and drilling machines, as a material for microtone knives for biological and medicinal uses, as a radiation detector, as a detector for temperature measurement, heat sink, as wire drawing dye, stylus for phonographs, hardness indenters, and as optical windows in high pressure cells. Numerous approaches have been utilized in attempts to synthesize diamond for the above applications. The processes for synthesizing diamond results in the production of diamond particles (usually made by depositing the diamond onto diamond seed crystals) or large diamond masses grown by deposition and/or compaction of diamond particles. Due to these end uses and methods of making synthetic diamond, there has been no requirement for thin diamond films or for a process for making them.
The present invention is directed to solving the disadvantages of materials heretofore utilized as X-ray transmissive elements in devices in which X-ray radiation is generated, measured, transmitted or detected, such as energy-dispersive X-ray spectrometers (EDAX) and X-ray fluorescence spectrometers (XRF). The X-ray transmissive elements of these devices include the tube within which the X-rays are produced, windows through which the X-rays must enter or exit a sample-containing chamber, and the X-ray radiation detector. The two most prevalent X-ray transmissive window materials used are beryllium and specialized polymers, however both have various disadvantages. Beryllium is toxic and is difficult to form into shapes. It is also expensive, is corrosive to moisture (even at moisture concentrations as low as atmospheric moisture) and is subject to leakage (by helium, for example) when it is formed into a thin film. Helium and other inert gases are often used as carrier media within the sample chambers under a vacuum. In addition beryllium windows of practical thicknesses (5-8 mm) are opaque to X-rays emitted by light elements such as oxygen, nitrogen, carbon and boron, so such elements cannot be detected through a beryllium window.
Polymeric materials are usually fragile and are unstable in high temperature environments of those processes which are frequently used to fabricate and operate X-ray tubes and X-ray spectrometers. Polymeric materials are also difficult to clean with organic solvents following prolonged operational use.
It is therefore an object of the present invention to provide synthetic diamond films for use as X-ray transmissive elements.
It is yet another object of the present invention to provide a method for making X-ray transmissive films of synthetic diamond. It is yet another object to provide a method for fabricating X-ray transmissive diamond windows for X-ray instruments.
These and other objects of the present invention will be apparent to those skilled in the art from the following description of the preferred embodiments and from the appended claims.